tests added for the new linting check

Author: Charlie-XIAO

scripts/tests/test_validate_unwanted_patterns.py

@@ -375,3 +375,72 @@ def test_strings_with_wrong_placed_whitespace_raises(self, data, expected):
             validate_unwanted_patterns.strings_with_wrong_placed_whitespace(fd)
         )
         assert result == expected
+
+
+class TestNoDefaultNotUsedForTyping:
+    @pytest.mark.parametrize(
+        "data",
+        [
+            (
+                """
+def f(
+    a: int | NoDefault,
+    b: float | lib.NoDefault = 0.1,
+    c: pandas._libs.lib.NoDefault = lib.no_default,
+) -> lib.NoDefault | None:
+    pass
+"""
+            ),
+            (
+                """
+# var = lib.NoDefault
+# the above is incorrect
+a: NoDefault | int
+b: lib.NoDefault = lib.no_default
+"""
+            ),
+        ],
+    )
+    def test_nodefault_not_used_for_typing(self, data):
+        fd = io.StringIO(data.strip())
+        result = list(validate_unwanted_patterns.nodefault_not_used_for_typing(fd))
+        assert result == []
+
+    @pytest.mark.parametrize(
+        "data, expected",
+        [
+            (
+                (
+                    """
+def f(
+    a = lib.NoDefault,
+    b: Any
+        = pandas._libs.lib.NoDefault,
+):
+    pass
+"""
+                ),
+                [
+                    (2, "NoDefault is not used for typing"),
+                    (4, "NoDefault is not used for typing"),
+                ],
+            ),
+            (
+                (
+                    """
+a: Any = lib.NoDefault
+if a is NoDefault:
+    pass
+"""
+                ),
+                [
+                    (1, "NoDefault is not used for typing"),
+                    (2, "NoDefault is not used for typing"),
+                ],
+            ),
+        ],
+    )
+    def test_nodefault_not_used_for_typing_raises(self, data, expected):
+        fd = io.StringIO(data.strip())
+        result = list(validate_unwanted_patterns.nodefault_not_used_for_typing(fd))
+        assert result == expected